DOE OSTI2020
FeOOH crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are sixteen inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 47–53°. There are a spread of Fe–O bond distances ranging from 1.90–2.17 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with four FeO5 trigonal bipyramids and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.34 Å. In the third Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra, a cornercorner with one FeO5 trigonal bipyramid, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 48–61°. There are a spread of Fe–O bond distances ranging from 1.93–2.19 Å. In the fourth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one FeO4 tetrahedra, corners with four FeO5 trigonal bipyramids, an edgeedge with one FeO6 octahedra, and edges with two equivalent FeO5 trigonal bipyramids. There are a spread of Fe–O bond distances ranging from 1.97–2.22 Å. In the fifth Fe3+ site, Fe3+ is bonded to four O2- atoms to form distorted FeO4 tetrahedra that share corners with two FeO6 octahedra, corners with two FeO5 trigonal bipyramids, and an edgeedge with one FeO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 46–62°. There are a spread of Fe–O bond distances ranging from 1.87–2.01 Å. In the sixth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four FeO5 trigonal bipyramids, an edgeedge with one FeO6 octahedra, and edges with three FeO5 trigonal bipyramids. There are a spread of Fe–O bond distances ranging from 1.97–2.19 Å. In the seventh Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra, a cornercorner with one FeO5 trigonal bipyramid, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 49–57°. There are a spread of Fe–O bond distances ranging from 1.92–2.12 Å. In the eighth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one FeO4 tetrahedra, corners with three FeO5 trigonal bipyramids, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.17 Å. In the ninth Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 48–65°. There are a spread of Fe–O bond distances ranging from 1.85–2.18 Å. In the tenth Fe3+ site, Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with four FeO5 trigonal bipyramids and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.21 Å. In the eleventh Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra, a cornercorner with one FeO5 trigonal bipyramid, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 44–56°. There are a spread of Fe–O bond distances ranging from 1.93–2.12 Å. In the twelfth Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share a cornercorner with one FeO4 tetrahedra, corners with two FeO5 trigonal bipyramids, and edges with three FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.91–2.16 Å. In the thirteenth Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra, a cornercorner with one FeO4 tetrahedra, a cornercorner with one FeO5 trigonal bipyramid, and an edgeedge with one FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–52°. There are a spread of Fe–O bond distances ranging from 1.90–2.19 Å. In the fourteenth Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share a cornercorner with one FeO6 octahedra, corners with five FeO5 trigonal bipyramids, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 71°. There are a spread of Fe–O bond distances ranging from 1.91–2.07 Å. In the fifteenth Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with three FeO6 octahedra, a cornercorner with one FeO5 trigonal bipyramid, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of Fe–O bond distances ranging from 1.88–2.24 Å. In the sixteenth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three FeO5 trigonal bipyramids and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.11 Å. There are sixteen inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.70 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the third H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.03 Å) and one longer (1.56 Å) H–O bond length. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.72 Å) H–O bond length. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the seventh H1+ site, H1+ is bonded in a distorted linear geometry to two O2- atoms. There is one shorter (1.04 Å) and one longer (1.60 Å) H–O bond length. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.73 Å) H–O bond length. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to two O2- atoms. There is one shorter (1.01 Å) and one longer (1.73 Å) H–O bond length. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the fourteenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the fifteenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the sixteenth H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are thirty-two inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two Fe3+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Fe3+ atoms. In the fifth O2- site, O2- is bonded in a T-shaped geometry to two Fe3+ and one H1+ atom. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe3+ and one H1+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to three Fe3+ atoms. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to two Fe3+ and one H1+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to three Fe3+ and one H1+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Fe3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted water-like geometry to two Fe3+ and one H1+ atom. In the fourteenth O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the fifteenth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Fe3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Fe3+ atoms. In the seventeenth O2- site, O2- is bonded in a 1-coordinate geometry to two Fe3+ and one H1+ atom. In the eighteenth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to three Fe3+ and one H1+ atom. In the nineteenth O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the twentieth O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the twenty-first O2- site, O2- is bonded in a 2-coordinate geometry to two Fe3+ and one H1+ atom. In the twenty-second O2- site, O2- is bonded in a distorted single-bond geometry to two Fe3+ and one H1+ atom. In the twenty-third O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Fe3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Fe3+ atoms. In the twenty-fifth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Fe3+ and one H1+ atom. In the twenty-sixth O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the twenty-seventh O2- site, O2- is bonded in a distorted single-bond geometry to two Fe3+ and one H1+ atom. In the twenty-eighth O2- site, O2- is bonded in a trigonal planar geometry to three Fe3+ atoms. In the twenty-ninth O2- site, O2- is bonded in a 3-coordinate geometry to two Fe3+ and one H1+ atom. In the thirtieth O2- site, O2- is bonded in a distorted single-bond geometry to two Fe3+ and one H1+ atom. In the thirty-first O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the thirty-second O2- site, O2- is bonded in a trigonal planar geometry to three Fe3+ atoms.